Catalog

ESE 2180 · Junction physics

P–N Junction Carrier Dynamics

Diffusion dumps majority carriers into the other side. Recombination uncovers ions. The ions build a field from N toward P until drift cancels diffusion. Bias then tilts that balance.

Equilibrium

Si-like · Eg = 1.12 eV · ni(300 K) = 1.5×1010 cm−3

Thermal motion is live. Cyan dots are electrons; crimson rings are holes. Hover the slice for recombination, uncovered ions, drift, and diffusion.

Carrier slice · x = −L → +L

electrons holes + donors − acceptors ℰ from N → P

A · Energy bands E(x)

Parabolic bending across depletion. One EF at Va = 0; split by qVa under bias.

B · Space charge ρ(x) and |ℰ|(x)

Step charge ±qN. Field is the integral — a triangle peaking at x = 0.

C · n(x), p(x) · log scale

Majorities sit at NA / ND. Minorities follow the law of the junction at the depletion edges.

Live depletion math

Abrupt, fully depleted, non-degenerate Si teaching model. Particle counts are logarithmic stand-ins, not 1016 dots. The existing diode lab still owns the circuit Q-point.